The role of DNA gyrase in maintaining bacterial chromosome structure will be investigated by use of specific inhibitors of gyrase, coumermycin and oxolinic acid. We intend to determine if gyrase binds at specific nucleotide sequences and whether it also is responsible for supertwisting plasmid DNA in vivo. In addition, we intend to explore the effects of these drugs on DNA synthesis in repair and recombination deficient mutants to understand how gyrase-drug damage in DNA is repaired.